Therefore you will need to have the Crossbow in order to kill them, before diving down to the other part of the broken boat for the loot. However below the water lurks several level 10 Drowners, and you can't use your swords in the water. You can spot the place by looking for a broken boat still floating on the water. This one in particular is just East of the Nilfgaardian Garrison, in the middle of a large part of the river. The map marker may say Spoils of War, but it's really just more guarded treasure. You can also find Witcher Gear here that will unlock the Side Quest: Scavenger Hunt: Viper School Gear. Enter the crypt and defeat him, then cast enough light to find the various treasure chests located within. Getting him to half health will cause him to retreat - whereupon you must follow him by blasting down the door with the Aard Sign. There will likely be a level 7 Wraith guarding the Place of Power out front. Travel North from White Orchard across the river and enter the cemetery. This guarded treasure may look like it is behind the White Orchard Graveyard, when in fact it is beneath the ground in the crypt. There are two chests here, both with randomized loot of great quality.

the huts in question are on top of a ridge in the Ransacked Village, where below, a few Drowners have killed those trying to bury (or unearth) the chests. This guarded treasure isn't listed when visiting a notice board, instead you'll have to explore to find it on your own (or find a note mentioning a buried treasure site below two burned huts). The main treasure can be found next to the wrecked boat in a large chest. there is at least one explosive barrel you can use to your advantage - otherwise try and lure them in small groups. A group of Drowners patrol this wrecked cargo boat, and can be quite tough. This guarded treasure is located South of White Orchard along the riverbank on the same side as the town.

Witcher 3 skellige interactive map